The aim of this study is to elucidate the relationship between the fiber structure and the heat of wetting of synthetic fibers, which is one of the important factors affecting the comfort of clothing. To this end, the heat of wetting of some commercial synthetic fibers having high water absorbency was measured using an adiabatic calorimeter constructed in our laboratory, in addition to the moisture regain, the water content and the amount of bound water. It was found that（1）the relationship between the water content and the moisture regain is very different among the studied fibers,（2）the heat of wetting of the fibers has a close relation with the moisture regain and the amount of bound water, but not with water content, and（3）carboxyl groups are about ten times more effective than hydroxyl groups in promoting the water absorbability of synthetic fibers.

DESCENTE SPORTS SCIENCE Vol.21/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE